Screw press



Nov. 22, 1960 R. H. MOKEE 2,960,926

SCREW mass Filed Oct. 2, 1957 2 Sheets-Sheet 1 IN V EN TOR.

TTOZA/EY Nov. 22, 1960 R. H. MCKEE 2,960,926

SCREW PRESS Filed Oct. 2, 1957 2 Sheets-Sheet 2 INVENT R.

ATTOENEY 2,960,926 Patented Nov. 22, 1960 SCREW PRESS Ralph H. McKee, New York, N.Y., assignor to lVlcKee Development Corp., New York, N.Y., a corporatlon of New York Filed Oct. 2, 1957, Ser. No. 687,747

6 Claims. c1. 10o 117 This invention relates to a screw press.

It is an object of this invention to provide a press for removing fibrous pulp from an aqueous suspension of said pulp.

It is another object to provide a screw press having an axis of a rotating element disposed in a vertical position.

It is another object to provide a screw press wherein the separation of pulp from the aqueous suspension of pulp is aided by gravitational force.

It is yet another object to provide a screw press of inexpensive construction.

It is a further object to provide a press which will inexpensively remove paper pulp from an aqueous suspension of said pulp.

These and other objects of this invention will become apparent upon reading the following disclosure taken in conjunction with the accompanying drawing showing illustrative embodiments of this invention.

In the drawing:

Fig. l is a vertical section view of the invention showing a rotatable cone shaped spindle disposed within stationary bar elements disposed in the configuration of a truncated cone,

Fig. 2 is a transverse section taken on line 2-2 of Fig. 1,

Fig. 3 is a schematic side view of the invention showing the cone shape formed by the plurality of stationary bars,

Fig. 4 is a view taken on line 4-4 of Fig. 3,

Fig. 5 is an end view of a stationary mixer blade,

Fig. 6 is a side view of the blade of Fig. 5,

Fig. 7 is a top view of a holding band used to hold the cone forming elements in place, and

Fig. 8 is a modification showing the use of a cylindrical spindle disposed within the cage of the cone forming bar elements.

Referring to the drawing and especially to Fig. 1, the screw press of this invention comprises a spindle 10 disposed in a cone shaped cage 11 (Fig. 3) formed by a plurality of spaced-apart bars 12 of a polygonal crosssection.

As shown in Figs. 2 and 3, the bars 12 are preferably rectangular in cross section and sloped away from the vertical plane so as to form a truncated cone. In other words, the cage 11 formed by the inwardly sloping bars 12 has a smaller diameter at the top than at the bottom.

Preferably the bars 12 are of square cross section and are disposed in a channeled bottom retainer ring 13 and a channeled top retainer ring 14. The bars are spaced from one another by suitable blocks 15. Blocks 15 are of the same thickness as bars 12 so that the cone 11 has a smooth inner wall surface. The blocks 15 are preferably spaced equally far from one another so that the length of the apertures between two adjacent bars 12 are equally long. The aperture openings in cage 11 are of rectangular configuration. Optionally the rectangular apertures of cone cage 11 may be other than of equal length. Thus the aperture lengths may be greatest at the bottom of the cone cage 11 adjacent ring 13 and gradually diminish as the apertures approach top ring 14..

Clearly, because of the cone shape of cage 11, although all the apertures between two adjacent bars may be of equal length, nevertheless the areas of the apertures adjacent bottom ring 13 are larger than the areas of the apertures adjacent top ring 14. Clearly, the blocks 15 are somewhat wedge shaped (Fig. 3) or truncated triangles.

Preferably blocks 15 are truncated isosceles triangles having parallel top and bottom edges and equal sides sloping equally toward one another.

The channel of both the top ring 14 and of the bottom ring 13 is sloped suitably inwardly to the respective ring center and function so as to retain bars 12 at the desired slope forming the cone of cone cage 11.

The plurality of cage bars 12 disposed in the respective channels of retainer rings 13 and 14 form the cone cage 11. The bars 12 are held rigidly together by means of circular retainer bands 16. The bands 16 may be integral circular elements but preferably they are made from a pair of semi-circular elements easily disengaged from one another. The manner of securing the respective pair of semi-circular elements forming a band 16 may be conventional mating clasps (Fig. 7) or any other suitable means such as a nut and bolt combination.

As shown in Fig. 1, the rings 16 are thickest and strongest at the top of the cage 11 adjacent ring 14 where the pressure on bars 12 is the reatest.

At the bottom of cage 11, the retainer rings 16 are relatively thin, since the pressure on bars 12 in this area is small as will be explained hereinafter.

A plurality of suitably long spacer bars 17 are disposed between the rings 16, after the rings 16 have been rammed into place upon bars 12, to prevent the rings 16 from sliding upwardly toward the small end of the cage 11 adjacent ring 14.

The cage 11 is secured removably at its top to a centrally apertured support ring 18 by means of a plurality of bolts placed in suitable bolt receiving apertures which bolts are then threaded into top ring 14.

The bottom of cage 11 is removably secured to a suitable circular base plate 20 provided with a plurality of holes through which bolts 21 pass and which are then threaded into bottom ring 13.

Base plate 20 is provided with a stud 22 having a cup cavity therein. Plate 20 is further provided with a pulp stock inlet opening in which inlet conduit 23 is secured.

An annular shell 24 having a top flange 25 and a bottom flange 26 is disposed around the cage 11. As shown in Fig. l, flange 25 is suitably apertured and is hermetically secured to support ring 18 by bolts 19, and flange 26 is also suitably apertured and is also hermetically secured to base plate 20 by bolts 21. Gaskets may be used with flanges 25 and 26, if desired, in order to obtain hermetical sealing.

The shell 24 functions as a tank and is provided with an effluent opening adjacent flange 26 in which an effluent conduit 27 is disposed.

The spindle 10 of the screw press is provided with the configuration of a truncated cone and comprises a conical surface element or cone wall 28 made of suitable metal, into the bottom of which is secured as by press fit a centrally apertured plate 29. A suitable pivot pin is disposed in the aperture of plate 29 and disposed in the cup cavity of stud 22. As shown in Fig. l, the pivot pin is an integral pin consisting of a nose portion 30 having a semi-circular end disposed in the semi-circular cavity of stud 22 and an integral shank portion fixedly fitted into the aperture of plate 29. Optionally, other conventional thrust bearings may be used. The axis of the shank 31 is the axis of the spindle l0 and its cone wall 28.

The cone wall 28 is provided at its top opening with a fixedly secured plate 32, said plate 32 being integral with an axle 33. The axis of axle 33 is also the axis of the spindle and its cone wall 28.

A plurality of suitably triangular flights 34 are slopingly secured at a right angle to the exterior surface of cone wall 28. As shown in Figs. 1 and 8, the spacing between flights increases as one goes from the top of the spindle 10 to the bottom of the spindle. Thus the successive flights 34 are spaced from one another in horizontal relationship about the cone wall, with the vertical spacing between flights increasing as one goes from the top of the spindle to the bottom of the spindle.

The slope of the flights 34 engaging cone wall 28 preferably is equal to about 30 of the circumference of the cone, although the contacting slope of a flight 34 disposed peripherally upon the cone wall may be varied widely, for example, it may cover 60 of the cone periphery.

As shown in Figs. 1 and 8 the flights 34 are disposed closely to bars 12 and function much like the conventional curved snow shovel in pushing pulp stock upwardly in cage 11.

Where the angle of the cone wall 28 is equal to the cone angle formed by bars 12. the cone surface of wall 28 is at all times equidistant from bars 12, in this case all the broad edges 35 of the triangular flights 34 are of the same length. However, as shown in Fig. 8 the spindle 10X may be provided with a cylindrical peripheral wall 36, in which case the retreating edges 37 of flights 34 increase in length as one goes from the top of the spindle 10X toward the bottom of the spindle 10X, in order to maintain a suitable uniform close clearance to bars 12.

It has been noticed that at times the pulp tends to be rotated within cage 11 rather than to be pushed vertically upward. To avoid possible rotation of the pulp, especially in the upper part of the cage, a plurality of horizontally disposed mixer blades 38 are secured to suitably spaced apart bars 12. The blades 38 are located in spaced vertical and horizontal relationship within the cage 11 and are so disposed that they pass equidistant between two adjacent flights 34. As shown in Fig. l, the blades extend toward the spindle wall in suitable space relationship thereto, to effect an eflicient mixing of the pulp located between the spindle and the cage wall.

As shown in Figs. 5 and 6, the blades 38 are preferably provided with a knife edge 39 disposed toward the direction of rotation of the spindle. The blades 38 are of integral construction and comprise a mixer portion and an integral threaded stud portion. The threaded stud is disposed in a threaded hole in a suitable bar 12. in lieu of a knife edge 39, the blade may have a round edge, or the blade may be a cylindrical rod.

The pulp is forced out of the top of the screw press between the axle 33 and the wall of the central aperture of plate 18 and against a self regulating spring-loaded collar 40. The collar 40 is an annular ring having a central aperture whose wall is disposed in sliding nontilting relationship against axle 33.

An integral circular collector pan 41 having a sloping lower wall 42 and a horizontal top wall 43, is provided with a horizontal flange 44 integral with the bottom of the sloping wall 42. Flange 44 is provided with suitable apertures through which are passed bolts 45. Bolts 45 are secured in suitable threaded holes located in ring 18.

The top wall 43 of the pan 41 is provided with an aperture through which axle 33 extends.

The collar 40 is provided with a sloped edge 46 of an angle equal to that of sloped wall 42 of pan 41, so that when the screw press is not operating the springloaded collar 40 is urged against the inner surface of wall 42.

As shown in Fig. l, the collar 40 is provided with a plurality of rods 47 threaded therein. The rods 47 are disposed through suitable apertures disposed in pan wall 43 and extend a suitable distance above the wall 43. The rods 47 are provided with fixed flanges 48 located above pan wall 43. A retaining cover plate 49 is provided with a central aperture through which axle 33 passes and also suitable apertures to receive movable rods 47. Cover plate 49 is circular and is provided with a ledge 50 having suitable apertures therein through which screws 51 are passed and secured in pan wall 43. A coil spring 52 of suitable strength is disposed upon each rod flange 48 and against the underside of cover plate 49. A collector pan 41 is provided with an outlet spout 53 through which pressed pulp of about 40 percent dry consistency is pushed.

In operation of the press a pulp suspension of about 2 to 6 percent or more consistency is passed into the press through conduit 23. The water is forced out through the larger apertures between bars 12 located adjacent bottom ring 13 forming a water level in the lower part of shell 24.

The pulp is pushed upwardly in the cage 11 by the rotation of the spindle 10 since the flights 34 push the pulp much as dew a moving snow shovel. The expressed water drains by gravity into the bottom of shell 24 and is removed from outlet 27 under some pressure as the air above the water level is somewhat compressed due to the force of the incoming stock suspension in conduit 23. The shell 24 may be modified by an opening for compressed air adjacent element 25 to provide needed air pressure on the surface of the water in shell 24 when a plurality of presses are used in a series relationship.

As the pulp is pushed up the cage 11 it is mixed by stationary blades 38 and forced against collar 40 causing compression of springs 52. The greater the compressive strength of the springs the higher is the consistency of the pulp stock at spout S3. The spring qualities are chosen so as to give a pulp at spout 53 of preferably 40 percent consistency, i.e. 60 percent water.

The bars 12 are preferably square with right angle corners. These corners may be used to deflber cooked pulp chips. Where cooked pulp is conducted directly to a screw press of this invention, the screw press preferably has its bars 12 slightly turned into the direction of rotation of spindle 10 in order to disintegrate or deflber the cooked wood chips. Where a plurality of screw presses are used in a washing series, only the first press receiving cooked stock has its bars turned slightly to expose a defibering longitudinal edge to the upwardly moving pulp.

The bars 12 are preferably made of stainless steel to withstand corrosive cooking liquors. Where neutral cooking liquor for pulping wood is used, one may use bars of common steel or steel plated with chromium.

Optionally, the spacing between bars may be made larger and the water removal faster by selectively bending the bars 12 outwardly and providing a larger bottom ring 13 to retain the bent bars.

The capacity of this screw press is also increased by increasing the circumference and/ or height of the spindle and its co acting cage.

An important advantage of this vertical screw press over a horizontal screw press is that the pulp consistency is gradually and uniformly increased from about 2 percent at the bottom of the cone to 40 percent at the top of the cone, since gravity uniformly draws all the expressed water down the outside of the cone cage 11.

This uniform consistency condition in a plane perpendicular to the screw axis is not possible in the prior art where the screw or spindle is horizontally disposed, since cellulose is more dense than water and tends to settle out to the bottom side of the horizontal press. The result is that in a horizontal press the consistency at the top is less than that vertically below it and adjacent the inside bottom wall of the press.

It is therefore seen that applicant has also a novel process of pressing liquid from a pulp.

The following is an illustration of a process using four screw presses; a continuous digester for cooking wood chips having a exit temperature of 300 F. at 100 pounds per square inch was valved at the digester outlet so as to pass cooked stock continuously through a water jacketed conduit to produce hot water for washing purposes and cooked stock having a temperature of 180 F. and 60 pounds per square inch. This cooled stock was continuously conducted into a first screw press whose blades were set so as to defiber the cooked chips.

The liquor expressed from the pulp in this first screw press is used concentrated cooking liquor and may be re-used as such in the hydrotropic process or the chemioals therein may be recovered by conventional means where non-hydrotropic cooking is used.

The 40 percent consistency hydrotropic pulp from this first screw press is conducted into a tank where is it diluted with a solution of about 12 percent hydrotropic salt and a mildly alkaline solution of caustic soda to prevent precipitation of lignin on the pulp fibers, as would be the case if water alone were used.

The alkaline diluted pulp suspension is then pumped through a disk refiner and into a second screw press where the mildly alkaline solution of lignin is removed at the bottom and a washed stock of 40 percent consistency is removed at the top. This lignin solution from the second press is sent to a recovery unit for subsequent use.

The 40 percent washed pulp from the second screw press is diluted in a tank with wash water from the fourth screw press and it is pumped into the bottom of the third screw press, where the wash water is removed. The 40 percent consistency pulp from the third screw press is passed into another dilution tank and diluted with the hot water obtained from cooling the digester stock mentioned previously.

The diluted hot water pulp suspension is then passed into the fourth screw press where the recovered 40 percent consistency pulp is passed to the paper mill or to the bleaching operation or to storage as brown stock.

Where conventional batch digesters using blow tanks are employed, a trash pump is used to convey the pulp suspension to the first screw press.

The use of the screw presses in conjunction with the various wood cooking processes to produce wood pulp is subject to wide variation depending on the type of process i.e. hydrotropic, sulfite, sulfate, semi-chemical pulp, etc., as well as for the type of wood used and kind of pulp to be made.

Any conventional means for driving axle 33 may be used, such as a gear secured thereto and driven by a chain, or the gear secured to axle 33 may be a silent helical gear driven by a worm gear.

Many other modifications of this invention, such as inverting of the equipment used with a top feed will become apparent to those skilled in the art, are included in the scope of this invention, though they are not the preferred form or modification.

If desired, for example, a plow or other pushing means may be secured to axle 33 within pan 41 to facilitate pushing the pulp into and through outlet spout 53.

Obviously this invention is of generic scope and such scope is intended to be embraced within the claims herein.

I claim:

1. An easily disassembled screw press for removing liquid from suspensions of fibrous material comprising a plurality of substantially vertically disposed and equally spaced-apart bars of rectangular cross sections forming a cage disposed in the configuration of a cone; an annular top retaining ring having a suitable depending sloped walled circular channel therein receiving the top ends of said bars; an annular bottom retaining ring having a suitable substantially upright sloped walled channel therein receiving the bottom ends of said bars; a plurality of suitable wedge shaped spacers of rectangular cross section having parallel horizontal top and bottom walls con nected to opposed side walls of equal slope disposed suitably in spaced-apart relationship between each pair of adjacent spaced-apart bars; band means for retaining said bars in place in said cage; a spindle disposed in said cage; a plurality of spirally disposed flights of triangular configuration secured along one edge to said spindle, said flights being spirally disposed in increasingly closer spiral relationship in going from the bottom of the spindle to the top of the spindle and said flights being disposed in creasingly closer in vertical relationship in going from the bottom of the spindle to the top of the spindle; bottom plate means having an inlet aperture for fiber containing suspension secured to the bottom of said cage; top plate means having a central outlet aperture for expressed fibers of about 40 percent consistency secured to the top of said cage; axle means rigidly secured to the top of said spindle; bearing means secured to the bottom of said spindle and journaled into said bottom plate means; and a cylindrical container having centrally apertured top and bottom walls hermetically secured respectfully to said top plate means and said bottom plate means, said container having an outlet opening for liquid adjacent its bottom wall.

2. The screw press of claim 1 wherein said band means consists of a plurality of spaced-apart annular rings of increasing thickness from the bottom of the cage to the top of said cage, said annular rings being spaced increasingly closer together from the bottom of the cage to the top of said cage and spacers bars disposed between said rings for retaining them immoveably in place.

3. The screw press of claim 2 wherein said spindle is cylindrical and said triangular flights are of decreasing width from the bottom of the spindle toward the top of the spindle thereby maintaining a uniform clearance between said flights and the bars forming the cone shaped cage.

4. The screw press of claim 2 comprising spring loaded annular means disposed about said axle means and secured to said top plate means for controlling the flow of expressed stock from said press.

5. The screw press of claim 1 comprising a cone shaped pulp collector pan disposed over the central outlet aperture and self-regulating spring-loaded means disposed in said pan continuously urging against the pulp forced out of the outlet.

6. The screw press of claim 5 wherein the self-regulating means comprises a slidable annular collar, a cover plate secured to the top of the collector pan in spaced relationship to the pan, said pan having a top wall, a plurality of guide rods secured to said collar and passed through the collector pan top wall and the cover plate secured thereto, said guide rods having fixed flanges disposed above said pan, and a coil spring disposed on each flange and against the cover plate for continuously urging the collar toward the inner cone wall of the pan.

References Cited in the file of this patent UNITED STATES PATENTS 239,222 Burgess Mar. 22, 1881 366,165 Gray July 5, 1887 641,266 Bussells Jan. 16, 1900 1,151,186 Johnson Aug. 24, 1915 1,245,950 Neufeldt Nov. 6, 1917 1,321,351 Anderson Nov. 11, 1919 1,876,064 Lang Sept. 6, 1932 2,118,992 Upton May 31, 1938 2,709,957 Armstrong June 7, 1955 2,730,242 Samuel Jan. 10, 1956 FOREIGN PATENTS 108,545 Great Britain Aug. 16, 1917 634,303 France Nov. 9, 1927 703,370 France Feb. 16, 1931 

